U.S. Navy Seeks To Streamline Communications, Reduce Antenna Clutter
A profusion of radomes and antennas clutter the masts and upperworks of many modern warships. Below decks, multiple consoles produced by many manufacturers support different communications networks, each with its own unique purpose. And in the electronic spectrum, all those networks compete for bandwidth to communicate with offboard systems.
Streamlining and reducing those antennae and consoles and greatly increasing bandwidth and electronic performance is the goal of Navy Multiband Terminal (NMT), a competition under way to provide U.S. Navy ships and submarines with a better communications grid.
“Commonality in operations and concept and better performance” is the project’s objective, said Capt. John Pope, the NMT program manager for the Space and Naval Warfare Systems Command (SPAWAR) in San Diego.
Raytheon’s Network Centric Systems, Marlborough, Mass., and Harris Corp .’s Government Communications Systems Division, Melbourne, Fla., are in the midst of a three-year effort to develop an NMT system for the Navy. Both competitors passed critical design reviews last spring, and SPAWAR plans to select one of the systems in fiscal 2007 for introduction into the fleet.
Under the contracts issued in October 2003, the NMT system is to replace existing communications systems on surface ships, submarines and Navy shore stations. New antennas are being developed for surface ships, Pope said, while shore and submarine installations will use antennas already in service.
The total value of Raytheon’s current contract is $1.66 billion while the Harris award could be worth up to $1.47 billion. The use of a number of existing Raytheon antenna designs in both NMT systems accounts for the price difference, Pope said.
Like a slow dial-up user of the Internet getting access to a T-1 line, introduction of the new system is expected to dramatically accelerate the transmission of data.
“You’ll be going from about 512 kilobytes a second on current terminals to 2 megabytes,” Pope said. “That’s pure performance to move imagery and data.”
One key to the new system will be its military encryption.
“The Advanced Extremely High Frequency of NMT will give over four times the protected bandwidth,” said Glen Basset, Raytheon’s NMT program manager.
The new NMT antennas being developed for surface ships will be stabilized to maintain connectivity with satellites in weather conditions up to Sea State 6, where waves are from 14 to 29 feet in height.
“Sea State 6 is a huge challenge,” Basset said. “The antennas have to point at the satellite within four one-hundredths of a degree.”
Two NMT antennas will be fitted to each ship, fore and aft, on opposite corners of the superstructure. The placement enables at least one of the antennas to “see” a satellite at all times, whichever way the ship is moving.
“That’s a very challenging problem,” Bassett said. “It requires very tight control of the antennas. If you can’t point them accurately you lose the link, and all that through-put that you need for intelligence information, decision-making and sending commands gets used up in resending information or requesting a resend.”
The solution is a switching system that alternates between antennas within one nanosecond, Basset said.
A similar concept has been developed to multiply use of the system’s bandwidth.
“With more users the ‘pipe’ gets very tight,” Basset said. “You need a bandwidth allocation system that can automatically reassign that bandwidth as people need it. The Navy has developed the TIP — Time Division Multiple Interface Processor — to give you TDMA , Time Division Multiple Access,” he said. By “dynamically changing information on the fly, many times a second, you can get more efficient use of the limited bandwidth the warfighter has in the theater of operations.”
Software and system architecture being developed for NMT also will be portable, Basset said, allowing it to be run on other systems. “It’s open architecture, using open standards,” he said. “Any developer could use it to develop their own radios.”
NMT is to replace a host of existing extremely high frequency terminals, including the WSC-6 family of terminals, Pope said. Streamlining multiple communications systems also will simplify training, Pope said, and will reduce the need for spare parts for different systems.
The smallest ship to be fitted with NMT under the current Navy requirements is a destroyer, primarily for cost reasons, Pope said. But Basset said Raytheon already has developed an antenna system that can work aboard a Littoral Combat Ship or even a 331-ton patrol boat.
“We’ve shown the Navy it can be done, now they have to validate the requirement,” Basset said, adding that the system could be scaled down to fit on a Coast Guard 136-ton or 170-ton patrol boat.
Although Harris provided an information sheet on their NMT program, company officials declined requests to talk about their efforts.